JP2019083116A - Lithium composite metal compound, positive electrode active material for lithium secondary batteries, positive electrode for lithium secondary batteries, and lithium secondary battery - Google Patents

Abstract

To provide a lithium composite metal compound with a high cycle retention rate, a positive electrode active material for lithium secondary batteries using the lithium composite metal compound, a positive electrode for lithium secondary batteries, and a lithium secondary battery.SOLUTION: This lithium composite metal compound is represented by composition formula (I). If Lrefers to the crystallite diameter that has a diffraction peak within the range of 2θ=18.7±1° and Lrefers to the crystallite diameter that has a diffraction peak within the range of 2θ=64.5±1° in powder X-ray diffraction measurement using a Cu-Kα ray, the ratio of Lto L, namely L/L, satisfies L/L≤1.3.SELECTED DRAWING: None

Description

  The present invention relates to a lithium composite metal compound, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

  The lithium composite metal compound is used as a positive electrode active material for a lithium secondary battery. Lithium secondary batteries are already in practical use not only for small power sources such as mobile phone applications and notebook personal computer applications, but also for medium and large power sources such as automotive applications and power storage applications.

The crystal structure of the lithium composite metal compound participates in the desorption of lithium from the positive electrode during charge and the insertion of lithium during discharge.
For this reason, in order to improve the battery characteristics of a lithium secondary battery using a lithium composite metal compound, an attempt has been made to control the crystal structure.
For example, Patent Document 1 aims to reduce the life characteristics, initial charge efficiency and initial resistance of a lithium secondary battery, and the crystallite size of the (003) plane relative to the crystallite size of the (110) plane of the lithium composite metal compound. A lithium composite metal compound powder is described which includes a composition having a ratio of 1.0 or more and less than 2.5.

International Publication No. 2014/136760

In order to further improve the battery characteristics such as the cycle maintenance rate, the lithium composite metal compound still has room for improvement.
The present invention has been made in view of the above circumstances, and is directed to a lithium composite metal compound having a high cycle retention under high voltage with an upper limit voltage of 4.45 V, and a lithium secondary battery using the lithium composite metal compound. An object is to provide a positive electrode active material, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

That is, the present invention includes the inventions of the following [1] to [8].
[1] A lithium composite metal compound represented by the following composition formula (I), which is calculated from a diffraction peak within a range of 2θ = 18.7 ± 1 ° in powder X-ray diffraction measurement using a CuKα ray the crystallite diameter is defined as L _a, 2θ = 64.5 when the crystallite size calculated from the diffraction peak in the range of ± 1 ° is defined as L _b, the ratio between the said L _a L _b (L _A lithium mixed metal compound, wherein _a / L _b ) is such that L _a / L _b ≦ 1.3.
_{Li [Li x (Ni (1} -y-z) Co y M z) 1-x] O 2 (I)
(Wherein M is at least one metal element selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Zn, Sn, Zr, Ga, Nb and V, −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.3, 0 ≦ z ≦ 0.2)
[2] The lithium mixed metal compound according to [1], wherein L _b is 600 Å ≦ L _b ≦ 800 Å.
[3] BET specific surface area of 3.0 m ² / g or less exceed 0.4 m ² / g, a lithium composite metal compound according to [1] or [2].
[4] The method according to any one of [1] to [3], wherein the amount of lithium hydroxide contained in the lithium composite metal compound determined as a conversion value from the result of neutralization titration is 0.3% by mass or less Lithium complex metal compounds.
[5] The lithium mixed metal compound according to any one of [1] to [4], which satisfies 0 <x ≦ 0.2 in the composition formula (I).
The positive electrode active material for lithium secondary batteries which has a lithium complex metal compound as described in any one of [6] [1]-[5].
The positive electrode for lithium secondary batteries which has a positive electrode active material for lithium secondary batteries as described in [7] [6].
The lithium secondary battery which has a positive electrode for lithium secondary batteries as described in [8] [7].

  According to the present invention, a lithium composite metal compound having a high cycle retention under high voltage with an upper limit voltage of 4.45 V, a positive electrode active material for a lithium secondary battery using the lithium composite metal compound, and a lithium secondary battery A positive electrode and a lithium secondary battery can be provided.

It is a schematic block diagram which shows an example of a lithium ion secondary battery.

In the present specification, the "specific surface area" is a value measured by the BET (Brunauer, Emmet, Teller) method. In the measurement of the specific surface area, nitrogen gas is used as the adsorption gas.
In the present specification, “crystallite diameter” refers to powder X-ray diffraction measurement using CuKα as a radiation source and a measurement range of diffraction angle 2θ of 10 ° or more and 90 ° or less, 2θ = 18.7 ± 1 ° Scherler formula L = Kλ / B cosθ (L: crystallite diameter, K: Scherrer constant, B: peak half width) Calculate the diffraction peak of the range and the diffraction peak of 2θ = 64.5 ± 1 °. The crystallite diameter can be calculated by using. It is a conventionally used method to calculate the crystallite size from this formula (for example, "X-ray structural analysis-determine the arrangement of atoms-" Apr. 30, 2002, 3rd edition, Wasao Yoshio, Matsubara Eiichiro, see).
In the present specification, the notation “Li” indicates that the element is not elemental Li but the element Li unless otherwise noted. The same applies to the other elements such as Ni, Co and Mn.
In the present specification, composition analysis of the lithium composite metal compound is performed by inductively coupled plasma analysis (hereinafter referred to as ICP). In addition, the ratio of elements of the lithium composite metal compound is a value in the lithium composite metal compound before the first charge (also referred to as activation treatment).

<Lithium complex metal compound>
The present invention is a lithium composite metal compound represented by the following composition formula (I), which is calculated from a diffraction peak within the range of 2θ = 18.7 ± 1 ° in powder X-ray diffraction measurement using CuKα ray is the crystallite diameter is defined as L _a, when the crystallite diameter calculated from the diffraction peak in the range of 2θ = 64.5 ± 1 ° is defined as L _b, and the L _a and said L _b The lithium composite metal compound is characterized in that the ratio (L _a / L _b ) is L _a / L _b ≦ 1.3.
_{Li [Li x (Ni (1} -y-z) Co y M z) 1-x] O 2 (I)
(Wherein M is at least one metal element selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Zn, Sn, Zr, Ga, Nb and V, −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.3, 0 ≦ z ≦ 0.2)

The “L _a ” is a crystallite diameter determined from a peak in the range of 2θ = 18.7 ± 1 ° in powder X-ray diffraction measurement using a CuKα ray. When the lithium composite metal compound has a hexagonal crystal structure belonging to the space group R-3m, La has a crystallite diameter in the [003] direction.
The “L _b ” is a crystallite diameter determined from a peak in the range of 2θ = 64.5 ± 1 ° in powder X-ray diffraction measurement using a CuKα ray. When the lithium composite metal compound has a hexagonal crystal structure belonging to the space group R-3m, Lb has a crystallite diameter in the [018] direction.

[L _a / L _b ]
Lithium mixed metal compound according to the present embodiment, the ratio of the said _{L a L b (L a /} L b) is _L a / _{L b} ≦ 1.3. _{L a} / L _b is preferably 1.29 or less, more preferably 1.28 or less, particularly preferably 1.27 or less. The lower limit value of L _a / L _b is not particularly limited, and is, for example, 0.1 or more and 0.2 or more and 0.3 or more.
The above upper limit value and lower limit value of L _a / L _b can be arbitrarily combined.

Lithium composite metal compound of the present embodiment is a L _{a /} L _b ≦ 1.3, isotropic is high crystallite structure. According to the study of the present inventors, it is found that a lithium composite metal compound having high isotropy with L _a / L _b ≦ 1.3 has a high cycle maintenance rate under a high voltage with an upper limit voltage of 4.45 V. It was done.

[Composition Formula (I)]
The lithium composite metal compound of the present embodiment is represented by the following composition formula (I).
_{Li [Li x (Ni (1} -y-z) Co y M z) 1-x] O 2 (I)
(Wherein M is at least one metal element selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Zn, Sn, Zr, Ga, Nb and V, −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.3, 0 ≦ z ≦ 0.2)

X
From the viewpoint of obtaining a lithium secondary battery having a high cycle maintenance rate, x in the formula (I) is preferably -0.1 or more, more preferably -0.05 or more, and particularly preferably more than 0. In addition, from the viewpoint of obtaining a lithium secondary battery with higher initial coulombic efficiency, x in the formula (I) is preferably 0.2 or less, more preferably 0.08 or less, and 0.06 or less It is further preferred that
The upper limit value and the lower limit value of x can be arbitrarily combined.
In the composition formula (I), x more preferably satisfies 0 <x ≦ 0.2.

Y
Further, in view of obtaining a lithium secondary battery having low battery resistance, y in the formula (I) is more preferably more than 0, and still more preferably 0.05 or more. Y in the formula (I) is preferably 0.3 or less, more preferably 0.29 or less, and still more preferably 0.28 or less.
The upper limit value and the lower limit value of y can be arbitrarily combined.

・ Z
Further, from the viewpoint of obtaining a lithium secondary battery having a high cycle maintenance rate, z in the formula (I) is preferably 0 or more, and more preferably 0.03 or more. Further, z in the formula (I) is preferably 0.2 or less, more preferably 0.18 or less, and still more preferably 0.17 or less.
The upper limit value and the lower limit value of z can be arbitrarily combined.

  M in the composition formula (I) is at least one selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Zn, Sn, Zr, Ga, Nb and V Represents a metal element. From the viewpoint of obtaining a lithium secondary battery having a high cycle maintenance rate, M is preferably at least one metal selected from the group consisting of Mn, Ti, Mg, Al, W, B, and Zr, and Mn, It is preferable that it is at least one metal selected from the group consisting of Al, W, B, and Zr.

[600 Å ≦ L _b ≦ 800 Å]
Lithium mixed metal compound according to the present embodiment, in a powder X-ray diffraction measurement using CuKα ray, when the crystallite size calculated from the diffraction peak in the range of 2θ = 64.5 ± 1 ° was L _b, 600 Å It is preferable that ≦ L _b ≦ 800 Å.

From the viewpoint of cycle retention rate to obtain a high lithium secondary battery, wherein _{L b} is preferably at least 600 Å, more preferably at least 610A, more 620Å is particularly preferred. In addition, 800 Å or less is preferable, 790 Å or less is more preferable, and 780 Å or less is particularly preferable. The upper limit value and the lower limit value of L _b can be arbitrarily combined.

[BET specific surface area]
In the present embodiment, BET specific surface area of the lithium composite metal compound ^(m 2 / g) is preferably from 3.0 m ² / g or less, more preferably 2.9 m ² / g or less, 2.8 m ² / g or less Particularly preferred. The lower limit value is preferably more than 0.4 m ² / g, more preferably 0.5 m ² / g or more, and still more preferably 0.6 m ² / g or more.
The upper limit value and the lower limit value of the BET specific surface area (m ² / g) of the lithium composite metal compound can be arbitrarily combined.
BET specific surface area of the lithium composite metal compound of the present embodiment is preferably not more than 0.4 m ² / g to over 3.0 m ² / g.

[Amount of lithium hydroxide]
In the present embodiment, from the viewpoint of facilitating the handling of the positive electrode active material when the positive electrode active material for lithium secondary battery is used, the amount of lithium hydroxide determined as a conversion value from the result of neutralization titration of the lithium composite metal compound is It is preferable that it is 0.3 mass% or less, 0.20 mass% or less is more preferable, and 0.15 mass% or less is especially preferable.

(Layered structure)
The crystal structure of the lithium composite metal compound is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The crystal structure of hexagonal _{type, P3, P3 1, P3 2} , R3, P3, R3, P312, P321, P3 1 12, P3 1 21, P3 2 12, P3 2 21, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 _{3 , P6, P6 / m, P6} 3 / m, P622, P6 1 22, P6 5 22, P6 2 22, P6 4 22, P6 3 22, P6mm, P6cc, P6 3 cm, P6 3 mc, P- 6m2, P-6c2, P- 62m, attributed to _{P-62c, P6 / mmm,} P6 / mcc, P6 3 / mcm, P6 3 / any one space group selected from the group consisting of mmc.

In addition, the crystal structure of monoclinic type is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2 / m, P2 ₁ / m, C2 / m, P2 / c, P2 ₁ / c, C2 / It belongs to any one space group selected from the group consisting of c.

  Among them, from the viewpoint of obtaining a lithium secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m, or a monoclinic type belonging to C2 / m. Particularly preferred is a crystal structure.

 The lithium compound used in the present invention is lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium hydroxide, lithium oxide, lithium oxide, lithium chloride, lithium fluoride and any one or a mixture of two or more is used. can do. Among these, one or both of lithium hydroxide and lithium carbonate are preferable.

<Method for producing lithium composite metal compound>
The method for producing a lithium composite metal compound of the present invention comprises the steps of producing a metal composite compound containing nickel, cobalt and M, and producing a lithium composite metal compound using the metal composite compound and a lithium compound. preferable.

In producing the lithium composite metal compound of the present invention, first, a metal composite compound comprising an essential metal composed of a metal other than lithium, that is, Ni, Co, or an essential metal composed of Ni, Co, and Any one or more metal selected from Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V (hereinafter referred to as "optional metal M" Prepare a metal complex compound containing Then, the metal complex compound is calcined with an appropriate lithium salt.
As a metal complex compound, metal complex hydroxide or metal complex oxide is preferable.
Below, an example of the manufacturing method of a positive electrode active material is divided and demonstrated to the manufacturing process of a metal complex compound, and the manufacturing process of a lithium complex metal compound.

(Manufacturing process of metal complex compounds)
The metal complex compound can be produced by a generally known batch coprecipitation method or continuous coprecipitation method. Hereinafter, the method for producing the same will be described in detail by taking a metal composite hydroxide containing nickel, cobalt and an optional metal M as a metal as an example.

First co-precipitation method, in particular by a continuous method described in 2002-201028 JP-nickel salt solution, cobalt salt solution, is reacted salt of any metal M solution, and complexing _agents, Ni a _Co b _{M c} A composite metal hydroxide represented by (OH) ₂ (wherein, a + b + c = 1) is produced.

The nickel salt which is a solute of the above-mentioned nickel salt solution is not particularly limited, and, for example, any of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate can be used. As a cobalt salt which is a solute of the above-mentioned cobalt salt solution, any of cobalt sulfate, cobalt nitrate and cobalt chloride can be used, for example. The above metal salts are used at a ratio corresponding to the composition ratio of the above Ni _a Co _b M _c (OH) ₂ . Also, water is used as a solvent.

  The complexing agent is capable of forming a complex with an ion of nickel, cobalt and an optional metal M in an aqueous solution, and examples thereof include ammonium ion donors (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride and the like), Hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine are included.

  During the precipitation, an alkali metal hydroxide (eg, sodium hydroxide, potassium hydroxide) is added, if necessary, to adjust the pH value of the aqueous solution.

In addition to the above-mentioned nickel salt solution, cobalt salt solution, and salt solution of optional metal M, when the complexing agent is continuously supplied to the reaction vessel, nickel, cobalt, and optional metal M are reacted to obtain Ni _a Co _b M _c (OH) ₂ is produced. During the reaction, the temperature of the reaction vessel is controlled, for example, in the range of 20 ° C. to 80 ° C., preferably 30 ° C. to 70 ° C., and the pH value in the reaction vessel is, for example, pH 9 to pH 13 or less, preferably pH 10 to pH 13 The materials in the reaction vessel are appropriately stirred while being controlled within the following range. The reaction vessel is of the type which causes the formed reaction precipitate to overflow for separation.

  Control of the finally obtained lithium composite metal compound to a desired physical property by appropriately controlling the concentration of the metal salt supplied to the reaction tank, the stirring speed, the reaction temperature, the reaction pH, the baking conditions described later, etc. it can.

  After the above reaction, the obtained reaction precipitate is washed with water and then dried to isolate a nickel cobalt optional metal M hydroxide as a composite compound of nickel cobalt optional metal M. Moreover, you may wash | clean with the alkaline solution containing weak acid water, sodium hydroxide, and potassium hydroxide as needed. In the above example, a composite hydroxide of nickel-cobalt optional metal M is produced, but a composite oxide of nickel-cobalt optional metal M may be prepared. When preparing a composite oxide of nickel-cobalt arbitrary metal M from a composite hydroxide of nickel-cobalt arbitrary metal M, oxidation is performed by calcinating at a temperature of 300 ° C. to 800 ° C. for 1 hour to 10 hours and oxidizing A process may be implemented.

(Production process of lithium complex metal compound)
-Mixing process After drying said metal complex oxide or hydroxide, it mixes with lithium salt.
As the lithium salt, any one or a mixture of two or more of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate and lithium oxide can be used.

 After drying of the metal composite oxide or hydroxide, classification may be performed as appropriate.

Main Firing Step A composite oxide of lithium-nickel cobalt optional metal M is obtained by firing a metal composite hydroxide of nickel cobalt optional metal M or a mixture of a composite metal oxide and a lithium salt. This firing step is referred to as "main firing step". In addition, dry air, an oxygen atmosphere, an inert atmosphere etc. are used according to a desired composition for baking, and the main baking process which has a several heating process if needed is implemented.

  The firing temperature of the metal complex oxide or hydroxide and the lithium compound such as lithium hydroxide or lithium carbonate is not particularly limited, but is preferably 650 ° C. or more and 1100 ° C. or less, and 690 ° C. or more and 1050 ° C. It is more preferable that it is ° C or less, and more preferably 700 ° C or more and 1025 ° C or less.

 The firing time is preferably 3 hours or more and 50 hours or less. When the firing time exceeds 50 hours, the volatilization of lithium tends to substantially deteriorate the battery performance. If the firing time is less than 3 hours, crystal growth will be insufficient and battery performance will tend to deteriorate.

In the present embodiment, by carrying out the main firing step at the above-described firing temperature and firing time, the L _a / L _b can be controlled to 1.3 or less, and a fired product having a highly isotropic crystal structure is obtained. It can be formed.

-Cleaning process It is preferable to implement the washing process which wash | cleans a baked product after this baking process. By carrying out the washing step, lithium is removed from the crystal structure of the fired product, and it is considered that the isotropy of the crystallite is increased by the change in the structure.

 In the present embodiment, as a method of bringing the cleaning liquid and the baked product into contact with each other, a method of charging the baked product into the cleaning liquid and stirring, a method of applying the cleaning liquid to shower water and applying to the baked product, a wet cake of the baked product Are introduced into the washing solution and stirred (re-slurry, re-pulp).

Slurry concentration In the present embodiment, it is preferable that in the washing step, the washing solution and the calcined product be mixed to form a slurry, and the calcined product powder be washed by stirring the slurry.
At that time, the concentration (slurry concentration) of the slurry in which the washing liquid and the calcined powder are mixed is not particularly limited, but it is preferably adjusted to 5% by mass or more, and more preferably 10% by mass or more. Moreover, adjusting to 65 mass% or less is preferable, and adjusting to 60 mass% or less is more preferable.

 By setting the slurry concentration in the above range, lithium is appropriately eluted from the fired product, the crystal structure of the fired product is changed, and a lithium composite metal compound having a highly isotropic crystal structure can be formed. Furthermore, the BET specific surface area and the amount of lithium hydroxide of the lithium composite metal compound can be controlled within the preferable range of the present invention.

In the present embodiment and the like .. washing time, the washing liquid used in the washing process, for example, water, and alkali solution. In the present embodiment, water is preferred.
In the present embodiment, the cleaning time is not particularly limited, but it is preferably 1 minute or more, more preferably 5 minutes or more, from the viewpoint of sufficiently removing the impurities. Moreover, from a viewpoint of suppressing excessive washing | cleaning, 60 minutes or less are preferable, and 30 minutes or less are more preferable.
Moreover, 0 degreeC or more and 30 degrees C or less are preferable, and, as for the temperature of the wash water used for washing | cleaning, 5 degrees C or more and 25 degrees C or less are more preferable.

 By setting the washing time or the like to the above conditions, lithium is appropriately eluted from the calcined product to change the crystal structure of the calcined product, and a lithium composite metal compound having a highly isotropic crystal structure can be formed. . Furthermore, the BET specific surface area and the amount of lithium hydroxide of the lithium composite metal compound can be controlled within the preferable range of the present invention. By carrying out the washing step, aggregation of the fired product is alleviated, so that the BET specific surface area can be increased.

··················································································································· In the present embodiment, when forming a slurry by mixing a cleaning liquid and a baked product, a method of injecting the baked powder into a stirred cleaning liquid is preferable.
At that time, from the viewpoint of preventing the sedimentation of the sintered powder, the charging speed of the baked powder to the washing solution is preferably 100 g / min or more to 1 L of washing solution, and from the viewpoint of uniforming washing, 3500 g / min to 1 L of washing solution The following are preferred.

 By setting the injection rate of the calcined powder to the washing liquid under the above conditions, it is possible to prevent excessive lithium elution from the calcined product, and a lithium composite metal compound having excellent cycle characteristics can be formed. Furthermore, the BET specific surface area and the amount of lithium hydroxide of the lithium composite metal compound can be controlled within the preferable range of the present invention.

Drying Step After the washing step, the fired product is separated from the washing solution by filtration or the like. Thereafter, the resultant is dried and pulverized, and then appropriately classified to obtain a lithium composite metal compound applicable to a lithium secondary battery.
In this embodiment, by drying the fired product after washing, it is possible to form a highly isotropic crystallite.
The temperature and method of the drying step are not particularly limited, but the drying temperature is preferably 30 ° C. or more, more preferably 40 ° C. or more, and more preferably 50 ° C. or more, from the viewpoint of sufficiently removing water. Is more preferred.
The temperature is preferably 300 ° C. or less, more preferably 250 ° C. or less, and still more preferably 200 ° C. or less, from the viewpoint of preventing formation of a heterophase on the surface of the lithium composite metal compound.

 The manufacturing method of a lithium complex metal compound may be equipped with the re-baking process after the said drying process. However, in the present embodiment, the lithium composite metal compound in which the anisotropic growth of crystallites is suppressed can be easily obtained by manufacturing with a manufacturing method that does not have the re-baking step.

<Lithium rechargeable battery>
Next, a positive electrode using the positive electrode active material for a lithium secondary battery of the present invention as a positive electrode active material of a lithium secondary battery and a lithium secondary battery having the positive electrode will be described while describing the configuration of the lithium secondary battery. Do.

  An example of the lithium secondary battery of the present embodiment includes a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution disposed between the positive electrode and the negative electrode.

  FIG. 1 is a schematic view showing an example of the lithium secondary battery of the present embodiment. The cylindrical lithium secondary battery 10 of the present embodiment is manufactured as follows.

  First, as shown in FIG. 1A, a pair of separators 1 having a strip shape, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-like negative electrode 3 having a negative electrode lead 31 at one end An electrode assembly 4 is formed by laminating and winding 2, the separator 1, and the negative electrode 3 in this order.

  Next, as shown in FIG. 1 (b), after the electrode assembly 4 and an insulator (not shown) are housed in the battery can 5, the can bottom is sealed, the electrode assembly 4 is impregnated with the electrolytic solution 6, An electrolyte is disposed between the negative electrode 3 and the negative electrode 3. Furthermore, the lithium secondary battery 10 can be manufactured by sealing the upper portion of the battery can 5 with the top insulator 7 and the sealing body 8.

  The shape of the electrode group 4 is, for example, a columnar shape such that the cross-sectional shape when the electrode group 4 is cut in the direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners. Can be mentioned.

  In addition, as a shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC60086 or JIS C 8500 which is a standard for a battery defined by the International Electrotechnical Commission (IEC) can be adopted. . For example, shapes such as a cylindrical shape and a square shape can be mentioned.

  Furthermore, the lithium secondary battery is not limited to the above-described wound-type configuration, and may have a stacked-type configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. So-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries can be exemplified as the laminated lithium secondary battery.

Hereinafter, each configuration will be described in order.
(Positive electrode)
The positive electrode of this embodiment can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.

(Conductive material)
A carbon material can be used as the conductive material of the positive electrode of the present embodiment. Graphite powder, carbon black (for example, acetylene black), fibrous carbon material etc. can be mentioned as a carbon material. Carbon black can increase the conductivity inside the positive electrode and improve the charge / discharge efficiency and output characteristics by adding a small amount to the positive electrode mixture, since fine particles have a large surface area, but if too much is added, it is due to the binder Both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture decrease, which causes an increase in internal resistance.

  The proportion of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. In the case of using a fibrous carbon material such as graphitized carbon fiber or carbon nanotube as the conductive material, it is possible to lower this ratio.

(binder)
A thermoplastic resin can be used as a binder which the positive electrode of this embodiment has. As this thermoplastic resin, polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene · hexafluoropropylene · vinylidene fluoride type Examples thereof include fluorine resins such as copolymers, hexafluoropropylene / vinylidene fluoride copolymers, and tetrafluoroethylene / perfluorovinyl ether copolymers; and polyolefin resins such as polyethylene and polypropylene.

  These thermoplastic resins may be used as a mixture of two or more. By using a fluorocarbon resin and a polyolefin resin as a binder, the proportion of the fluorocarbon resin to the whole of the positive electrode mixture is 1% by mass to 10% by mass, and the proportion of the polyolefin resin is 0.1% by mass to 2% by mass. A positive electrode mixture having high adhesion to the current collector and high bonding strength in the positive electrode mixture can be obtained.

(Positive current collector)
As a positive electrode current collector of the positive electrode of the present embodiment, a belt-like member made of a metal material such as Al, Ni, stainless steel or the like can be used. Among them, from the viewpoint of easy processing and low cost, it is preferable to use Al as the forming material and process it into a thin film.

  As a method of supporting the positive electrode mixture on the positive electrode current collector, a method of press-molding the positive electrode mixture on the positive electrode current collector can be mentioned. In addition, the positive electrode mixture is made into a paste using an organic solvent, and the obtained positive electrode mixture paste is applied to at least one side of the positive electrode current collector, dried, pressed and fixed, and the positive electrode current collector The mixture may be supported.

  When making a positive electrode mixture paste, as an organic solvent which can be used, amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; methyl acetate Ester solvents such as: dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP), and other amide solvents.

  Examples of a method of applying the paste of the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method and an electrostatic spray method.

A positive electrode can be manufactured by the method mentioned above.
(Negative electrode)
The negative electrode of the lithium secondary battery of the present embodiment may be capable of doping and dedoping lithium ions at a potential lower than that of the positive electrode, and a negative electrode mixture containing a negative electrode active material is supported on the negative electrode current collector And an electrode comprising only the negative electrode active material.

(Anode active material)
Examples of negative electrode active materials included in the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, or alloys, which can be doped and de-doped with lithium ions at a potential lower than that of the positive electrode. Be

  Examples of the carbon material that can be used as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers and an organic polymer compound fired body.

As an oxide which can be used as a negative electrode active material, an oxide of silicon represented by SiO ₂ , SiO such as SiO _x (here, x is a positive real number); TiO ₂ , TiO such as TiO such as TiO _x , x is an oxide of titanium represented by a positive real _{number); V 2 O 5, VO} 2 formula VO _x (wherein, etc., x is an oxide of vanadium represented by a positive real number); _Fe 3 _{O 4} Iron oxide represented by the formula FeO _x (where x is a positive real number) such as Fe ₂ O ₃ or FeO; SnO _x (where x is a positive real number) such as SnO ₂ or SnO Oxides of tin; WO ₃ , WO ₂ etc. oxides of tungsten represented by the general formula WO _x (where x is a positive real number); lithium and titanium such as Li ₄ Ti ₅ O ₁₂ , LiVO ₂ etc. Or a composite metal oxide containing vanadium; It is possible.

Sulfides usable as the negative electrode active material include sulfides of titanium represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS; V ₃ S ₄ , VS _2, VS equation VS _x (where x is a positive real number) Vanadium sulfide; Fe ₃ S ₄ , FeS ₂ , FeS equation FeS _x (where x is a positive real number) Sulfide of iron represented; Mo ₂ S ₃ , MoS ₂ formula MoS _x (where x is a positive real number) Molybdenum sulfide represented by the formula; SnS _2, SnS formula SnS _x (where x is represented sulfides of tin is a positive real number); WS ₂ wherein WS _x (wherein, etc., x is sulfides of tungsten represented by a positive real number); _Sb 2 _{S 3,} etc. formula SbS _x (wherein Where x is a positive real number) an antimony sulfide; Se ₅ S ₃ , SeS ₂ , SeS, and the like; SeS _x (where x is a positive real number); and sulfides of selenium.

As nitrides that can be used as the negative electrode active material, Li ₃ N, Li _3-x A _x N (where, A is either one or both of Ni and Co, and 0 <x <3). And lithium containing nitrides.

  These carbon materials, oxides, sulfides and nitrides may be used alone or in combination of two or more. Also, these carbon materials, oxides, sulfides and nitrides may be either crystalline or amorphous.

  Moreover, as a metal which can be used as a negative electrode active material, lithium metal, silicon metal, tin metal, etc. can be mentioned.

Examples of alloys usable as the negative electrode active material include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn and Li-Sn-Ni; silicon alloys such as Si-Zn; Sn-Mn and Sn It can also be mentioned; -Co, Sn-Ni, Sn -Cu, tin alloys such as _Sn-La; Cu 2 _Sb, alloys such as La 3 _Ni 2 Sn _7.

  These metals and alloys are mainly used alone as an electrode after being processed into, for example, a foil shape.

  Among the above-mentioned negative electrode active materials, the potential of the negative electrode hardly changes from the uncharged state to the fully charged state during charging (the potential flatness is good), the average discharge potential is low, and the capacity retention rate when repetitively charged and discharged is A carbon material mainly composed of graphite such as natural graphite and artificial graphite is preferably used because of high (the cycle characteristics are good) and the like. The shape of the carbon material may be, for example, a flaky shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

  The above-mentioned negative mix may contain a binder as needed. As a binder, a thermoplastic resin can be mentioned, Specifically, PVdF, thermoplastic polyimide, carboxymethylcellulose, polyethylene and polypropylene can be mentioned.

(Negative current collector)
As a negative electrode collector which a negative electrode has, the strip | belt-shaped member which uses metal materials, such as Cu, Ni, stainless steel, as a forming material can be mentioned. Among them, from the viewpoint that it is difficult to form an alloy with lithium and it is easy to process, it is preferable to use Cu as a forming material and process it into a thin film.

  As a method of supporting the negative electrode mixture on such a negative electrode current collector, similarly to the case of the positive electrode, a method by pressure molding, using a solvent etc. to make a paste is applied on the negative electrode current collector, dried and pressed. The method of crimping is mentioned.

(Separator)
As a separator which the lithium secondary battery of this embodiment has, for example, a form such as a porous film, a non-woven fabric, a woven fabric or the like made of a material such as polyolefin resin such as polyethylene and polypropylene, a fluorine resin, and a nitrogen-containing aromatic polymer The material which has can be used. Further, two or more of these materials may be used to form a separator, or these materials may be stacked to form a separator.

  In the present embodiment, the separator has a permeability resistance of 50 seconds / 100 cc or more, 300 seconds / 100 cc or more according to the Gurley method defined by JIS P 8117, in order to allow the electrolyte to permeate well during battery use (during charge and discharge). Or less, and more preferably 50 seconds / 100 cc or more and 200 seconds / 100 cc or less.

  The porosity of the separator is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The separator may be a laminate of separators having different porosity.

(Electrolyte solution)
The electrolytic solution of the lithium secondary battery of the present embodiment contains an electrolyte and an organic solvent.

As the electrolyte contained in the electrolytic solution, LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN _{(SO 2 CF 3) (COCF} 3), Li (C 4 F 9 SO 3), LiC (SO 2 CF 3) 3, Li 2 B 10 Cl 10, LiBOB ( wherein, BOB is, bis (oxalato) borate And LiFSI (where FSI is bis (fluorosulfonyl) imide), lower aliphatic carboxylic acid lithium salts, lithium salts such as LiAlCl _{4 and the} like, and mixtures of two or more of these. You may use Above all, as the electrolyte, at least one selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ It is preferable to use one containing one kind.

  The organic solvent contained in the electrolytic solution is, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di Carbonates such as (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2- Ethers such as methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylaceto Amides such as amides; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethylsulfoxide, 1,3-propanesultone or the like, or fluorocarbons introduced into these organic solvents ( The thing which substituted one or more among the hydrogen atoms which an organic solvent has with the fluorine atom can be used.

  As an organic solvent, it is preferable to mix and use 2 or more types of these. Among them, mixed solvents containing carbonates are preferable, and mixed solvents of cyclic carbonate and non-cyclic carbonate and mixed solvents of cyclic carbonate and ethers are more preferable. As a mixed solvent of cyclic carbonate and non-cyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. An electrolytic solution using such a mixed solvent has a wide operating temperature range, is not easily degraded even when charged and discharged at a high current rate, is not easily degraded even when used for a long time, and natural graphite as an active material of the negative electrode Even when a graphite material such as artificial graphite is used, it has many features of being hard to decompose.

Further, as the electrolytic solution, it is preferable to use an electrolytic solution containing a lithium salt containing fluorine such as LiPF ₆ and an organic solvent having a fluorine substituent, because the safety of the obtained lithium secondary battery is enhanced. Mixed solvents containing ethers with a fluorine substituent, such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether, and dimethyl carbonate have the capacity even if they are charged and discharged at high current rates It is more preferable because the maintenance rate is high.

A solid electrolyte may be used instead of the above-mentioned electrolyte solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound containing at least one or more of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which made the polymer compound hold | maintain a non-aqueous electrolyte can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 S-B 2 S 3, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS _{2 -Li 2 SO 4, Li 2} S-GeS 2 -P 2 S 5 inorganic solid electrolytes containing a sulfide, and the like, may be used a mixture of two or more thereof. By using these solid electrolytes, the safety of the lithium secondary battery may be further enhanced.

  In addition, in the case of using a solid electrolyte in the lithium secondary battery of the present embodiment, the solid electrolyte may play a role of a separator, and in such a case, the separator may not be required.

  Since the positive electrode active material having the above configuration uses the lithium composite metal compound of the present embodiment described above, the cycle maintenance at high voltage with the upper limit voltage of 4.45 V of the lithium secondary battery using the positive electrode active material is maintained The rate can be improved.

  In addition, since the positive electrode having the above-described configuration includes the above-described positive electrode active material for a lithium secondary battery of the present embodiment, it improves the cycle maintenance rate at a high voltage of 4.45 V as the upper limit voltage of the lithium secondary battery. be able to.

  Furthermore, since the lithium secondary battery having the above-described configuration has the above-described positive electrode, it becomes a secondary battery with a high cycle maintenance rate at a high voltage with the upper limit voltage of 4.45 V compared to the conventional one.

  The invention will now be described in more detail by way of examples.

 In the present example, evaluation of the lithium composite metal compound was performed as follows.

<Composition analysis>
The compositional analysis of the lithium composite metal compound produced by the method described below is carried out by dissolving the obtained powder of the lithium composite metal compound in hydrochloric acid and then inductively coupling plasma emission analyzer (SPS 3000 manufactured by SII Nano Technology Co., Ltd.) ) Was performed.

Determination of lithium hydroxide in lithium complex metal compounds (neutralization titration)
20 g of the lithium composite metal compound and 100 g of pure water were placed in a 100 mL beaker and stirred for 5 minutes. After stirring, the lithium composite metal compound was filtered, 0.1 mol / L hydrochloric acid was added dropwise to 60 g of the remaining filtrate, and the pH of the filtrate was measured with a pH meter. The titration amount of hydrochloric acid at pH = 8.3 ± 0.1 is AmL, and the titration amount of hydrochloric acid at pH = 4.5 ± 0.1 is BmL. According to the following formula, it is included in the lithium composite metal compound Lithium hydroxide concentration was calculated. In the following formulas, the molecular weight of lithium hydroxide was calculated as Li: 6.941, C: 12, O: 16,
Lithium hydroxide concentration (%) = 0.1 × (B−A) /1000×73.882/ (20 × 60/100) × 100

<Powder X-ray diffraction measurement>
The powder X-ray diffraction measurement was performed using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). The lithium composite metal compound powder is filled in a dedicated substrate, and measurement is performed using a Cu-Kα radiation source under the conditions of diffraction angle 2θ = 10 ° to 100 °, sampling width 0.03 °, and scan speed 20 ° / min. The powder X-ray diffraction pattern was obtained.
Using the integrated X-ray powder analysis software PDX1, powder crystallite diameter of the diffraction peaks _{L a} and within the range of X-ray diffraction pattern of 2θ = 18.7 ± 1 °, the range of 2θ = 64.5 ± 1 ° calculated crystallite size of the diffraction peak of the internal as _{L b,} and calculates a ratio between the said _{L a L b (L a /} L b).

<BET specific surface area measurement>
After 1 g of the lithium composite metal compound powder was dried at 105 ° C. for 30 minutes in a nitrogen atmosphere, it was measured using Macsorb (registered trademark) manufactured by Mountech Co. (unit: m ² / g).

[Fabrication of lithium secondary battery]
Preparation of Positive Electrode for Lithium Secondary Battery A lithium composite metal compound obtained by a manufacturing method described later is used as a positive electrode active material, and the positive electrode active material, a conductive material (acetylene black) and a binder (PVdF) are used for a lithium secondary battery. A paste-like positive electrode mixture was prepared by adding and kneading so as to have a composition of positive electrode active material: conductive material: binder = 92: 5: 3 (mass ratio). At the time of preparation of the positive electrode mixture, N-methyl-2-pyrrolidone was used as an organic solvent.

The obtained positive electrode mixture was applied to a 40 μm thick Al foil serving as a current collector and vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of this positive electrode for lithium secondary batteries was 1.65 cm ² .

Preparation of Lithium Secondary Battery (Coin-Type Cell) The following operation was performed in a dry air atmosphere glove box.
The positive electrode prepared in “Preparation of positive electrode for lithium secondary battery” is placed on the lower lid of a coin cell (manufactured by Hohsen Co., Ltd.) for coin-type battery R2032 with the aluminum foil surface facing downward, and the laminated film separator is thereon (The heat-resistant porous layer was laminated (thickness 16 μm) on the polyethylene porous film). Into this, 300 μL of an electrolyte was injected. The electrolyte used was prepared by dissolving LiPF ₆ in a 30:35:35 (volume ratio) mixed solution of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate so as to be 1.0 mol / L.
Next, using the metal lithium as the negative electrode, place the negative electrode on the upper side of the laminated film separator, cover the top through the gasket, caulking with a caulking machine, and lithium secondary battery (coin-type battery R2032. (Sometimes referred to as "battery").

・ Charge / discharge test [cycle test]
Using the coin-type battery produced in “Production of lithium secondary battery (coin-type cell)”, the life evaluation is carried out in 50 cycle tests under the conditions shown below, and the discharge capacity is maintained after 50 times The rate was calculated by the following equation. Note that the higher the discharge capacity retention rate after 50 times, the better the high voltage cycle characteristics are. Discharge capacity retention rate after 50 times (%) = 50th discharge capacity / 1st discharge capacity x 100
Hereinafter, the discharge capacity maintenance rate after 50 times may be described as a "cycle maintenance rate."

<Charge and discharge test conditions>
Test temperature: 25 ° C
Charge maximum voltage 4.45V, charge current 0.5CA, constant current constant voltage charge, end with 0.05CA current value Discharge minimum voltage 2.5V, discharge current 1.0CA, constant current discharge

Example 1
Production of Lithium Composite Metal Compound 1 [Manufacturing Process of Nickel Cobalt Aluminum Composite Hydroxide]
After water was introduced into the reaction vessel equipped with a stirrer and an overflow pipe, an aqueous solution of sodium hydroxide was added, and the liquid temperature was maintained at 58 ° C.

  An aqueous solution of nickel sulfate and an aqueous solution of cobalt sulfate were mixed such that the atomic ratio of nickel atoms to cobalt atoms was 0.80: 0.15, to prepare a mixed material solution.

  Next, the mixed raw material solution, a 24.2 mass% aqueous solution of aluminum sulfate and an aqueous solution of ammonium sulfate were continuously added as a complexing agent to the reaction vessel under stirring, and nitrogen gas was continuously ventilated. The flow rate of the aqueous solution of aluminum sulfate was adjusted so that the atomic ratio of nickel atom, cobalt atom and aluminum atom was 0.80: 0.15: 0.05. An aqueous solution of sodium hydroxide is added dropwise so that the pH of the solution in the reaction tank becomes 11.6, to obtain nickel-cobalt-aluminum composite hydroxide particles, which are washed with sodium hydroxide solution and then dewatered by a centrifugal separator, By releasing and drying at 105 ° C., a nickel-cobalt-aluminum composite hydroxide 1 was obtained.

[Oxidation process]
The nickel-cobalt-aluminum composite oxide 1 was obtained by firing the nickel-cobalt-aluminum composite hydroxide 1 at 650 ° C. for 5 hours.

[Mixing process]
The nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide powder obtained as described above were weighed and mixed so that Li / (Ni + Co + Al) = 1.07.

[Firing process]
Thereafter, the mixture obtained in the mixing step was fired at 780 ° C. for 6 hours in an oxygen atmosphere to obtain a fired product 1.

[Washing process]
Thereafter, the obtained baked product 1 was washed with water. In the washing step, 300 g of the baked product 1 is taken and added to stirred 300 g of pure water at a rate of 3000 g / min per 1 L of the washing liquid to form a slurry, and then the obtained slurry is stirred for 10 minutes to dehydrate. Went by.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 150 ° C. for 12 hours to obtain a lithium composite metal compound washed dry powder 1 (hereinafter referred to as lithium composite metal compound 1).

Evaluation of lithium composite metal compound 1 Composition analysis of the obtained lithium composite metal compound 1 was carried out, and when it was made to correspond to composition formula (I), x = 0.05, y = 0.15, z = 0.05, Met.

The L _a / L _b , the cycle retention rate (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 1 are described in Table 1.

(Example 2)
Production of lithium mixed metal compound 2 [Washing process]
The baked product 1 obtained above was washed with water. In the washing step, 300 g of the baked product 1 is taken and added to the stirred 700 g of pure water at a rate of 1285 g / min per liter of the washing solution to form a slurry, and then the obtained slurry is stirred for 10 minutes and dewatered. Went by.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 150 ° C. for 12 hours to obtain a lithium composite metal compound washed and dried powder 2 (hereinafter referred to as lithium composite metal compound 2).

Evaluation of lithium composite metal compound 2 Composition analysis of the obtained lithium composite metal compound 2 was carried out, and when it was made to correspond to the composition formula (I), x = 0.02, y = 0.15, z = 0.05 there were.

The L _a / L _b , the cycle maintenance factor (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 2 are described in Table 1.

(Example 3)
Production of Lithium Complex Metal Compound 3 [Manufacturing Process of Nickel Cobalt Aluminum Composite Hydroxide]
After water was introduced into a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous solution of sodium hydroxide was added, and the liquid temperature was maintained at 70 ° C.

  An aqueous solution of nickel sulfate and an aqueous solution of cobalt sulfate were mixed such that the atomic ratio of nickel atoms to cobalt atoms was 0.75: 0.20, to prepare a mixed material solution.

  Next, the mixed raw material solution, a 24.2 mass% aqueous solution of aluminum sulfate and an aqueous solution of ammonium sulfate were continuously added as a complexing agent to the reaction vessel under stirring, and nitrogen gas was continuously ventilated. The flow rate of the aqueous solution of aluminum sulfate was adjusted so that the atomic ratio of nickel atom, cobalt atom and aluminum atom was 0.75: 0.20: 0.05. An aqueous solution of sodium hydroxide is added dropwise so that the pH of the solution in the reaction tank becomes 11.0, to obtain nickel-cobalt aluminum composite hydroxide particles, which are washed with sodium hydroxide solution and then dewatered by a centrifugal separator, By releasing and drying at 105 ° C., nickel-cobalt-aluminum composite hydroxide 2 was obtained.

[Mixing process]
The nickel-cobalt-aluminum composite hydroxide 2 and the lithium hydroxide powder obtained as described above were weighed and mixed so that Li / (Ni + Co + Al) = 1.10.

[Firing process]
Thereafter, the mixture obtained in the mixing step was fired at 780 ° C. for 6 hours in an oxygen atmosphere to obtain a fired product 2.

[Washing process]
Thereafter, the obtained baked product 2 was washed with water. In the washing step, 4000 g of the baked product 3 is taken, added to the stirred 9333 g of pure water at a rate of 214 g / min per 1 L of the washing liquid, and after slurrying, the obtained slurry is stirred for 10 minutes and dewatered. Went by.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 150 ° C. for 8 hours to obtain a lithium composite metal compound washed dry powder 3 (hereinafter referred to as lithium composite metal compound 3).

Evaluation of lithium composite metal compound 3 Composition analysis of the obtained lithium composite metal compound 3 was carried out, and when it was made to correspond to the composition formula (I), x = −0.01, y = 0.20, z = 0.05 Met.

The L _a / L _b , the cycle maintenance factor (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 3 are described in Table 1.

(Example 4)
Production of Lithium Composite Metal Compound 4 [Manufacturing Process of Nickel Cobalt Aluminum Composite Hydroxide]
After water was introduced into the reaction vessel equipped with a stirrer and an overflow pipe, an aqueous solution of sodium hydroxide was added, and the liquid temperature was maintained at 45 ° C.

  An aqueous solution of nickel sulfate and an aqueous solution of cobalt sulfate were mixed such that the atomic ratio of nickel atoms to cobalt atoms was 0.88: 0.09, to prepare a mixed material solution.

  Next, under stirring, this mixed raw material solution, a 7.2% by mass aqueous solution of aluminum sulfate and an aqueous solution of ammonium sulfate were continuously added into the reaction vessel as a complexing agent, and nitrogen gas was continuously ventilated. The flow rate of the aqueous solution of aluminum sulfate was adjusted so that the atomic ratio of nickel atom, cobalt atom and aluminum atom was 0.88: 0.09: 0.03. An aqueous solution of sodium hydroxide is added dropwise so that the pH of the solution in the reaction tank becomes 12.1, to obtain nickel-cobalt-aluminum composite hydroxide particles, which are washed with sodium hydroxide solution and then dewatered by a centrifugal separator, The product was isolated and dried at 350 ° C. to obtain nickel cobalt aluminum composite hydroxide 3.

[Oxidation process]
The obtained nickel-cobalt-aluminum composite hydroxide 3 was calcined at 670 ° C. for 3 hours to obtain a nickel-cobalt-aluminum composite oxide 2.

[Mixing process]
The nickel-cobalt-aluminum composite oxide 2 and lithium hydroxide powder obtained as described above were weighed and mixed so that Li / (Ni + Co + Al) = 1.10.

[Firing process]
Thereafter, the mixture obtained in the mixing step was fired at 720 ° C. for 10 hours in an oxygen atmosphere to obtain a fired product 3.

[Washing process]
Thereafter, the obtained baked product 3 was washed with water. In the washing step, 4000 g of the baked product 3 is taken and added to the stirred 9333 g of pure water at a charging rate of 214 g / min per liter of the washing solution to form a slurry, and the obtained slurry is stirred for 20 minutes and dewatered. went.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 150 ° C. for 8 hours to obtain a lithium composite metal compound washed and dried powder 4 (hereinafter referred to as lithium composite metal compound 4).

Evaluation of lithium composite metal compound 4 Composition analysis of the obtained lithium composite metal compound 4 was carried out, and when it was made to correspond to the composition formula (I), x = 0.03, y = 0.09, z = 0.03, Met.

The L _a / L _b , the cycle retention rate (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 4 are described in Table 1.

(Comparative example 1)
Production of lithium mixed metal compound 5 [mixing step]
The above nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide powder were weighed and mixed such that Li / (Ni + Co + Al) = 1.10.

[Firing process]
Thereafter, the mixture obtained in the mixing step was fired at 780 ° C. for 6 hours in an oxygen atmosphere to obtain a fired product 4.

[Washing process]
Thereafter, the obtained baked product 4 was washed with water. The washing step is carried out by taking 4000 g of the baked product 4 and adding it to the stirred 9333 g of pure water at a rate of 214 g / min per liter of the washing liquid to form a slurry, stirring the obtained slurry for 10 minutes and dewatering. The

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 105 ° C. for 12 hours to obtain a lithium composite metal compound washed dry powder 5.

[Re-baking process]
Thereafter, the mixture was put into an oxygen atmosphere and re-baked at 780 ° C. for 5 hours to obtain a lithium composite metal compound refired powder 5 (hereinafter referred to as lithium composite metal compound 5).

Evaluation of lithium composite metal compound 5 Composition analysis of the obtained lithium composite metal compound 5 was carried out, and when it was made to correspond to the composition formula (I), x = 0.0, y = 0.15, z = 0.05 there were.

The L _a / L _b , the cycle retention rate (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 5 are described in Table 1.

(Comparative example 2)
Production of lithium mixed metal compound 6 [cleaning step]
The fired product 2 obtained above was washed with water. The washing step is carried out by taking 4000 g of the baked product 2 and adding it to the stirred 9333 g of pure water at a rate of 214 g / min per liter of the washing liquid to form a slurry and stirring the obtained slurry for 20 minutes and dewatering. The

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 105 ° C. for 12 hours.

[Re-baking process]
Thereafter, the mixture was put into an oxygen atmosphere and refired at 780 ° C. for 5 hours to obtain lithium composite metal compound refired powder 6 (hereinafter referred to as lithium composite metal compound 6).

Evaluation of lithium composite metal compound 6 Composition analysis of the obtained lithium composite metal compound 6 was carried out, and when it was made to correspond to the composition formula (I), x = 0.0, y = 0.20, z = 0.05 there were.

The L _a / L _b , the cycle retention rate (%), the BET specific surface area (unit: m ² / g), and the amount of lithium hydroxide of the lithium composite metal compound 6 are described in Table 1.

(Comparative example 3)
Production of lithium mixed metal compound 7 [mixing step]
The above nickel-cobalt-aluminum composite oxide 2 and lithium hydroxide powder were weighed and mixed so that Li / (Ni + Co + Al) = 1.05.

[Firing process]
Thereafter, the mixture obtained in the mixing step was fired at 700 ° C. for 10 hours in an oxygen atmosphere to obtain a fired product 5.

[Washing process]
Thereafter, the obtained baked product 5 was washed with water. In the washing step, 4000 g of the baked product 5 is collected, added to the stirred 9333 g of pure water at a charging rate of 214 g / min per 1 L of the washing liquid to form a slurry, and the obtained slurry is stirred for 20 minutes and dewatered. went.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 150 ° C. for 8 hours to obtain a lithium composite metal compound washed dry powder 7.
[Re-baking process]
Thereafter, the mixture was put into an oxygen atmosphere and refired at 760 ° C. for 10 hours to obtain a lithium composite metal compound refired powder 7 (hereinafter referred to as lithium composite metal compound 7).

Evaluation of lithium composite metal compound 7 Composition analysis of the obtained lithium composite metal compound 7 was carried out, and when it was made to correspond to the composition formula (I), x = 0.05y = 0.09, z = 0.03 The

The L _a / L _b , the cycle retention rate (%), the BET specific surface area (unit: m ² / g), and the lithium hydroxide amount (unit: mass%) of the lithium composite metal compound 7 are described in Table 1.

As described in Table 1 above, the lithium composite metal compounds of Examples 1 to 4 all had high cycle retention rates at high voltage of 85% or more. In contrast, beyond the L a _/ L _b is 1.3, Comparative Examples 1 and 2 which anisotropy seems highly crystalline structure, had lower cycle retention ratio at high voltages.

(Example 5)
Production of lithium mixed metal compound 8 [mixing step]
The above nickel-cobalt-aluminum composite hydroxide 2 and lithium hydroxide powder were weighed and mixed so that Li / (Ni + Co + Al) = 1.07.

[Firing process]
Thereafter, the mixture obtained in the above mixing step is fired at 780 ° C. for 6 hours in an oxygen atmosphere to obtain a sintered lithium composite metal compound powder 8 (hereinafter referred to as a lithium composite metal compound 8).

Evaluation of lithium composite metal compound 8 Composition analysis of the obtained lithium composite metal compound 8 was carried out, and when it was made to correspond to the composition formula (I), x = 0.07, y = 0.20, z = 0.05 there were.

The L _a , L _b and L _a / L _b of the lithium mixed metal compound 8 are described in Table 2.

(Example 6)
Production of lithium mixed metal compound 9 [cleaning step]
The lithium composite metal compound 8 was washed with water. In the washing step, 6970 g of the lithium composite metal compound 8 is taken and added to the stirred 16263 g of pure water at a charging rate of 171 g / min per 1 L of the washing solution to form a slurry, and the obtained slurry is stirred for 10 minutes and dewatered It went by.

[Drying process]
Thereafter, the wet cake obtained in the washing step was dried at 105 ° C. for 12 hours to obtain a lithium composite metal compound washed and dried powder 9 (hereinafter referred to as lithium composite metal compound 9).

Evaluation of lithium composite metal compound 9 Composition analysis of the obtained lithium composite metal compound 9 was carried out, and when it was made to correspond to the composition formula (I), x = −0.01, y = 0.20, z = 0.05 Met.

The L _a , L _b and L _a / L _b of the lithium mixed metal compound 9 are described in Table 2.

(Comparative example 4)
Production of lithium mixed metal compound 10 [re-baking step]
The lithium composite metal compound 9 was put in an oxygen atmosphere and refired at 780 ° C. for 5 hours to obtain a lithium composite metal compound recalcined powder 10 (hereinafter referred to as lithium composite metal compound 10).

Evaluation of lithium composite metal compound 10 Composition analysis of the obtained lithium composite metal compound 10 was carried out, and when it was made to correspond to the composition formula (I), x = −0.01, y = 0.20, z = 0.05 ,Met.

As in the results described in Table 2 above, Example 6 in which the washing and drying step was carried out after the main baking was smaller in L _a / L _b than in Example 5 in which the washing and drying step was not carried out. It was possible to form a highly crystalline crystal structure.
Moreover, after washing | cleaning drying, Comparative example 4 which implemented re-baking showed that L _a / L _b was large, and it turned out that the crystal structure with high anisotropy is formed.

 DESCRIPTION OF SYMBOLS 1 ... separator, 2 ... positive electrode, 3 ... negative electrode, 4 ... electrode group, 5 ... battery can, 6 ... electrolyte solution, 7 ... top insulator, 8 ... sealing body, 10 ... lithium secondary battery, 21 ... positive electrode lead, 31 ... Anode lead

Claims (8)

The lithium composite metal compound represented by the following composition formula (I), which is a crystallite diameter calculated from a diffraction peak within a range of 2θ = 18.7 ± 1 ° in powder X-ray diffraction measurement using a CuKα ray was defined as _{L a,} 2 [Theta] = 64.5 when the crystallite size calculated from the diffraction peak in the range of ± 1 ° is defined as _{L b,} the _{L a} and ratio of the _{L b (L} a / L _b ) lithium complex metal compound characterized in that L _a / L _b ≦ 1.3;
_{Li [Li x (Ni (1} -y-z) Co y M z) 1-x] O 2 (I)
(Wherein M is at least one metal element selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Zn, Sn, Zr, Ga, Nb and V, −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.3, 0 ≦ z ≦ 0.2) The lithium mixed metal compound according to claim 1, wherein L _b is 600 Å ≦ L _b ≦ 800 Å. BET specific surface area exceeds the 0.4 m ² / g, or less 3.0 ^m 2 / g, according to claim 1 or a lithium composite metal compound according to 2.  The lithium composite metal compound according to any one of claims 1 to 3, wherein an amount of lithium hydroxide contained in the lithium composite metal compound determined as a conversion value from a result of neutralization titration is 0.3% by mass or less. .  The lithium composite metal compound according to any one of claims 1 to 4, wherein 0 <x ≦ 0.2 is satisfied in the composition formula (I).   The positive electrode active material for lithium secondary batteries which has a lithium complex metal compound of any one of Claims 1-5.   The positive electrode for lithium secondary batteries which has a positive electrode active material for lithium secondary batteries of Claim 6.   The lithium secondary battery which has a positive electrode for lithium secondary batteries of Claim 7.

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